The Let Property Campaign: How to Disclose Undeclared UK Rental Income Before HMRC Writes First

The Let Property Campaign is HMRC's voluntary disclosure route for individuals with undeclared income from letting residential property. HMRC's guide lists the classic cases: a single buy-to-let, a portfolio, a room let above the Rent a Room threshold, holiday lettings, an inherited property kept and let, and people living abroad for more than six months who rent out UK property (Let Property Campaign guide, GOV.UK). There is no published end date: it is a standing facility, not a time-limited amnesty.

The exclusions matter. A landlord who holds the flat through a limited company must disclose through the company's own channels, not the campaign. And income from an overseas property is an offshore issue: the Worldwide Disclosure Facility exists for liabilities relating wholly or partly to income arising outside the UK or assets held outside the UK (WDF guidance, GOV.UK). Some landlords need both routes at once, run in parallel. Our guide to HMRC nudge letters and the Worldwide Disclosure Facility covers the offshore side.

The right route depends on what went wrong, how long ago, and where the income arose.

The amendment route is narrower than people hope: you usually have 12 months from the Self Assessment deadline to change a return, and beyond that you must write to HMRC, with overpayment relief claims limited to 4 years after the end of the tax year (Self Assessment corrections, GOV.UK). If you never registered for Self Assessment at all, there is nothing to amend, and the campaign is the route. For how landlord filing normally runs, see non-resident landlord tax and expat Self Assessment.

The number of years in a disclosure mirrors HMRC's assessment time limits: a normal limit of 4 years from the end of the relevant tax period, extended to 6 years where tax was lost carelessly, 12 years for offshore matters within income tax, capital gains tax and inheritance tax, and 20 years for deliberate behaviour and for failure to notify (CH53100 and CH53600, HMRC).

HMRC's campaign guide applies exactly this logic: 4 years with reasonable care, 6 if careless, up to 20 for failure to notify or deliberate behaviour. The sting is that the landlords most likely to need the campaign, the ones who never registered at all, are in the failure to notify category by definition, so every year of letting is potentially in scope.

Penalties are a percentage of the tax lost, and the percentage depends on your behaviour, on whether the disclosure was unprompted (you came forward with no reason to believe HMRC had found you) or prompted, and on the quality of the disclosure, scored on telling, helping and giving access to records. Penalties can reach 100% of the tax where the income arose in the UK and 200% for an offshore liability, but voluntary disclosure pulls the figure down dramatically, and where reasonable care was taken there is no penalty at all (Let Property Campaign guide, GOV.UK).

The inaccuracy ranges come from CH82470 and the failure to notify ranges from CH73520. Read the table from the taxpayer's side and the pattern is stark. A careless inaccuracy disclosed unprompted can be reduced to nil; the same error prompted starts at 15%. A landlord who never registered and comes forward unprompted, years late but cooperating fully, sits in a 10% to 30% band and can realistically achieve the 10% floor. Wait for the letter and the floor doubles to 20%, and once deliberate is in play the prompted minimum is 35%. HMRC's guide is explicit that people who do not come forward and are caught later face higher penalties or criminal prosecution.

The campaign is self-assessed from start to finish: you, or your adviser, work out the income, tax, interest and penalty, and put the whole package to HMRC as an offer (Let Property Campaign guide, GOV.UK).

Step 1, notify. You tell HMRC you want to take part and receive a disclosure reference number. A disclosure is only unprompted if you come forward with no reason to believe HMRC has found you, so notify before any HMRC letter arrives; the detailed number-crunching can follow.

Step 2, disclose within 90 days of HMRC's acknowledgement: rental income and allowable expenses for every year in scope, the tax, interest, and your penalty self-assessment with the behaviour category and reduction justified. The most recent tax year is usually handled through a normal return rather than the disclosure itself.

Step 3, make a formal offer for the full amount. Once HMRC accepts, offer and acceptance form a binding contract that settles those years.

Step 4, pay, with payment reaching HMRC by the same 90-day deadline. If you cannot pay in full, contact HMRC before submitting the disclosure so an instalment arrangement can be agreed rather than defaulting on the offer.

One warning built into the guidance: a disclosure is unlikely to be accepted where HMRC has already notified an intention to open an enquiry or compliance check. At that point early and full disclosure still influences the penalty, but the campaign terms are gone. The window closes when HMRC's letter lands, not when you get around to replying.

The most common disclosure client we see is not a UK landlord hiding income: it is someone who moved abroad years ago, kept the UK flat, and assumed that leaving the country ended their UK tax obligations. It did not. UK rental income stays taxable in the UK however long you are away, and HMRC treats you as a non-resident landlord once you live abroad for six months or more (GOV.UK). Under the Non-resident Landlord Scheme a letting agent or tenant should deduct basic rate tax from the rent unless HMRC has approved a form NRL1i application to receive it gross, and either way the income still belongs on a Self Assessment return.

Where it goes wrong is the private let with no agent: the tenant pays rent straight into a UK or overseas account, nobody deducts anything, no NRL1i was ever filed and no return was ever made. That is failure to notify, with the 20-year limit in principle, and it is exactly the fact pattern the campaign lists as eligible. Two features soften the blow. First, many non-residents can still claim the UK Personal Allowance (£12,570 in 2026/27): British citizens, EEA nationals, anyone who worked for the UK government in the year, and others where a double taxation agreement provides it (GOV.UK). In years where rental profit sat below the allowance, the liability can vanish entirely. Second, where basic rate tax was deducted under the scheme, it is credited against the bill. The disclosure also needs to look forwards: registering properly for Self Assessment, filing the current year, dealing with any 60-day CGT reporting if the plan is to sell, and Making Tax Digital once income crosses the thresholds.

Interest is charged on every disclosed year from the date the tax was originally due until it is paid, calculated daily. It is not a penalty and cannot be negotiated away. HMRC's late payment rate has been set at the Bank of England base rate plus 4% since 6 April 2025, and stands at 7.75% a year from 9 January 2026 (HMRC interest rates, GOV.UK). On a disclosure spanning six or seven years the earliest year has been accruing for the better part of a decade, and every month of hesitation adds interest across every year.

Take a landlord employed on £55,000 a year who inherited a flat in early 2019, let it from the start of the 2019/20 tax year, and never told HMRC. Rental profit after allowable expenses is £8,000 a year, and because her salary already fills the basic rate band, the rental profit is taxed at the higher rate of 40% throughout (bands per GOV.UK). In summer 2026 she comes forward before any HMRC contact. She never registered, so this is failure to notify and all six completed years, 2019/20 to 2024/25, go into the disclosure; 2025/26 is dealt with by registering for Self Assessment and filing a normal return.

Now run the counterfactual. HMRC identifies her first and writes. The disclosure is prompted, so the non-deliberate floor doubles to 20%, £3,840. Worse, six years of silence invites the argument that the failure was deliberate, and a prompted deliberate failure to notify carries a 35% to 70% penalty: £6,720 to £13,440 on the same tax, with a compliance check instead of a self-assessed offer. The tax and interest are identical in both worlds; the difference between coming forward and being found is measured in thousands of pounds and in who controls the process.

HMRC's standing position in the campaign guidance is blunt: tell us now, or face higher penalties or criminal prosecution if we find you later. Once a nudge letter or compliance check notification arrives, three things change at once. The disclosure becomes prompted, so every penalty floor rises. The behaviour assessment hardens, because years of ignored obligations are easier to paint as deliberate once HMRC is asking the questions. And you lose the campaign's self-assessed process in favour of an enquiry HMRC runs on its own timetable.

Coming forward unprompted keeps all three in your favour: bottom-of-range penalties, a credible non-deliberate position, and a contractual settlement you priced yourself. It also fixes the future cheaply, because registration, current-year filing and the Non-resident Landlord Scheme paperwork get sorted in the same exercise. Our guide to working with a UK tax adviser sets out where professional help earns its fee; a behaviour-and-penalty argument across six years of rental income is firmly in that category.

We run landlord disclosures end to end: establishing which years are in scope and why, rebuilding rental accounts from bank statements and letting records, claiming every allowable expense, computing tax and interest year by year, self-assessing the penalty with a reasoned behaviour position, and drafting the disclosure and offer so it is accepted first time. For non-residents we also put the go-forward position right: Self Assessment registration, the NRL1i application, and the annual returns.

Everything is on a fixed fee agreed upfront: personal returns from £350, non-resident and expat returns from £550, and complex work including disclosures from £750, with the exact fee quoted once we have seen the shape of the case. If HMRC has already written to you, speed matters; if they have not, that is the window to use. Start with a free 30-minute clarity call, or read about our Self Assessment service. One conversation is usually enough to tell you which route applies, how many years are in play, and what the settlement will roughly look like.